Dose variability in different lymph node levels during locoregional breast cancer irradiation: the impact of deep-inspiration breath hold.

Abstract

Aim of the present analysis was to evaluate the movement and dose variability of the different lymph node levels of node-positive breast cancer patients during adjuvant radiotherapy(RT) with regional nodal irradiation (RNI) in deep-inspiration breath hold (DIBH). Thirty-five consecutive node-positive breast cancer patients treated from October 2016 to February 2018 receiving postoperative RT of the breast or chest wall including RNI of the supra-/infraclavicular lymph node levels (corresponding to levelsIV, III, Rotter LN (interpectoral), and some parts of levelII) were analyzed. To evaluate the lymph node level movement, acenter of volume (COV) was obtained for each lymph node level for free-breathing (FB) and DIBH plans. Geometric shifts and dose differences between FB and DIBH were analyzed. Asignificant movement of the COV in anterior(y) and cranial(z) dimensions was observed for lymph node levelsI-II and Rotter lymph nodes (p < 0.001) due to DIBH. Only minor changes in the lateral dimension (xaxis) were observed, without reaching significance for levelsIII, IV, and internal mammary. There was asignificant difference in the mean dose of levelI (DIBH vs. FB: 38.2 Gy/41.3 Gy, p < 0.001) and levelII (DIBH vs. FB: 45.9 Gy/47.2 Gy, p < 0.001), while there was no significant difference in levelIII (p = 0.298), levelIV (p = 0.476), or internal mammary nodes (p = 0.471). Asignificant movement of the axillary lymph node levels was observed during DIBH in anterior and cranial directions for node-positive breast cancer patients in comparison to FB. The movement leads to asignificant dose reduction in levelI and levelII.